The compound (+)-(4R,5S,6S)-6-[(1R)-1-hydroxyethyl]-4-methyl-7-oxo-3[[(3S,5S)-5-(sulfamoylaminomethyl)pyrrolidin-3-yl]thio]-1-azabicyclo[3.2.0]hept-2-ene-2-carboxylic acid (hereinafter simply referred to as S-4661) having a structure represented by the formula below is a pyrrolidylthiocarbapenem derivative, which is a useful compound as an antimicrobial drug.

Note that this compound is also designated as “(4R,5S,6S)-3-[[(3S,5S)-5-(sulfamoylaminomethyl)pyrrolidin-3-yl]thio]-6-[(1R)-1-hydroxyethyl]-4-methyl-7-oxo-1-azabicyclo[3.2.0.]hept-2-ene-2-carboxylic acid” or “(1R,5S,6S)-6-[(1R)-1-hydroxyethyl]-2-[(3S,5S)-5-sulfamoylaminomethyl-1-pyrrolidin-3-yl]thio-1-methyl-1-carba-2-penem-3-carboxylic acid”.
S-4661 is described in Japanese Laid-Open Publication No. 5-294970. However, Japanese Laid-Open Publication No. 5-294970 describes only examples in which an amorphous form thereof was isolated. The amorphous solid of S-4661 has insufficient stability in storage, so that long-term storage under typical storage conditions disadvantageously leads to discoloration and a reduction in purity. Therefore, in order to develop S-4661 as a medicament, particularly an injection, a crystalline preparation having higher storage stability as compared to amorphous preparations is desired.
For this reason, a variety of crystals of S-4661 have been studied for improvements in storage stability, ease of handling, and the like of S-4661. As a result, a variety of crystals of S-4661 were confirmed.
For example, JP No. 2843444 discloses a type I crystal and a type II crystal of S-4661. The peaks of the type I crystal and type II crystal have characteristic diffraction angles (2θ) in X-ray diffraction as follows:
Type I: 7.32, 14.72, 18.62, 20.42, 21.1, 22.18, 23.88, and 29.76 (degrees) and
Type II: 6.06, 12.2, 14.56, 17.0, 18.38, 20.68, 24.38, 24.60, 25.88, and 30.12 (degrees)
(conditions for measurement of X-ray diffraction: CuKα ray, 1.54 Angstroms (monochromator), tube voltage 40 kV, tube current 40 mA).
However, in the art, a still further improvement in the stability of S-4661 has been desired.